DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage. Chevrolet PJJ 2000

For 1990-2009 cars
Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Intake Air Temperature (IAT) sensor uses a thermistor to control the signal voltage to the PCM. The PCM supplies a 5 V reference and a ground to the sensor. When the air is cold the resistance is high, therefore the IAT signal voltage will be high. If the intake air is warm, resistance is low, therefore the IAT signal voltage will be low.

### Conditions for Running the DTC

• | The engine run time is more than 320 seconds.

• | The vehicle speed sensor indicates that vehicle speed is more than 15 mph (24 km/h).

### Conditions for Setting the DTC

The IAT sensor signal voltage indicates that the intake air temperature is more than 128°C (262°F) for 12.5 seconds.

### Action Taken When the DTC Sets

• | The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with fault active.

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

• | A history DTC is stored.

• | Coolant fan turns ON.

• | The PCM will default to 60°C (140°F) for intake air temperature. The scan tool will not the show the defaulted value.

### Conditions for Clearing the MIL/DTC

• | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.

• | A history DTC will clear after 40 consecutive warm up cycles without a fault.

• | Use a scan tool to clear the DTCs.

### Diagnostic Aids

• | If the vehicle is at ambient temperature, compare the IAT sensor to the ECT sensor. The IAT sensor and the ECT sensor should be relatively close to each other.

• | Use the Temperature vs. Resistance Values table to evaluate the possibility of a skewed sensor. Refer to Temperature Versus Resistance .

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step simulates a DTC P0113 condition. If the scan tool displays the specified value, the IAT signal circuit and the PCM are OK.

2. Reprogram the replacement PCM and perform the Crankshaft Position System Variation Learn procedure.

#### DTC P0112-Intake Air Temperature (IAT) Circuit-Low Voltage

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Turn ON the ignition, with the engine OFF. Does the IAT sensor value measure greater than the specified value? | 128°C (262°F) | Go to Step 4 | Go to Step 3

3

1. Review the Freeze Frame data and record the parameters.
2. Start the engine.
3. Operate the vehicle within the Freeze Frame conditions and Conditions for Running the DTC as specified in the supporting text.

Does the IAT sensor value measure greater than the specified value?

128°C (262°F)

Go to Step 4

Go to Diagnostic Aids

4

1. Turn OFF the ignition.
2. Disconnect the IAT sensor connector.
3. Turn ON the ignition, with the engine OFF.

Does the IAT sensor value measure below the specified value?

-30°C (-22°F)

Go to Step 5

Go to Step 6

5

1. Turn OFF the ignition.
2. Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 10

--

6

1. Turn OFF the ignition.
2. Connect a test lamp to B+.
3. Probe the IAT sensor signal circuit terminal at the IAT sensor connector.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 9

7

1. Turn OFF the ignition.
2. Disconnect the PCM connector.
3. Connect a test lamp to B+.
4. Probe the IAT sensor signal circuit terminal at the IAT connector.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 9

8 | Repair the short to ground in the IAT sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 10 | --

9

1. Inspect for a poor connection at the PCM.

Important:: The replacement PCM must be programmed and the Crankshaft Position Variation procedure must be performed.

2. If the PCM connections are OK, replace the PCM. Refer to Powertrain Control Module Replacement/Programming and Crankshaft Position System Variation Learn .

Did you complete the replacement?

--

Go to Step 10

--

10

1. Use a scan tool to clear the DTCs.
2. Operate the vehicle within the Conditions for Running this DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK